Several sources for the production of x-rays have been developed. The electron-impact x-ray sources generally produce high energy x-rays which are difficult to control. Such x-rays, for example, are not usable in a lithography application. Synchrotron sources emit softer x-rays (extreme ultraviolet) but are limited by high cost and large physical dimensions. Laser produced x-rays are desirable, but heretofore, have yielded poor performance and efficiency and are difficult to control. Factors controlling x-ray emission from laser produced plasmas are not well understood. It has been suggested, theoretically, that mixed species targets might theoretically decrease duration of the x-ray emission. However, this technique has not been proven.
Accordingly, what is needed is a method and an apparatus for controlling laser produced x-rays to obtain acceptable x-ray conversion efficiency, very high x-ray brightness, and good control of the characteristics of the x-ray emission.